1. Field of the Invention
The invention relates to the field of signaling and/or lighting light-emitting devices for a motor vehicle. To be more precise, the invention relates to the field of the stop lights at the top of the rear window of a motor vehicle.
2. Description of the Related Art
For safety reasons, a motor vehicle is generally fitted with an additional stop light centrally positioned at the rear. When the driver of the motor vehicle applies the brakes, this light is therefore lit and attracts the attention of following road users. Being disposed at a raised position, for example in the upper part of a rear window, this stop light becomes visible by a queue of uses. As a result, more successive users are informed of the change of speed of the driver who is applying the brakes ahead of them. They are therefore better able to anticipate the dangers, and traffic conditions become safer.
To improve its visibility whilst preserving the useable volume of the passenger compartment of the motor vehicle, the stop light may be installed in known manner in the opening panel of the trunk when the latter means that the rear window can pivot. If the rear window is fixed, the stop light may be attached to the sealing of the passenger compartment. The stop light extends vertically downward from its support. It shines through the rear window of the vehicle that receives it, whilst remaining discreet in the passenger compartment.
For a given motor vehicle type or model, it is known to develop a type of stop light in a rear central position. Such a device generally includes one or more optical lenses associated with one or more light sources, for example of light-emitting diode (LED) type. The electronic circuit including the light sources is generally supported by a printed circuit mounted at a predetermined location in the device. It is in fact not desirable to provide a plurality of devices for different configurations of the same vehicle model, notably for reasons of production efficiency and associated development costs.
For reasons of the regulations, notably where the intensity of the perceived flux of the stop lights is concerned, it is often necessary to use LEDs of different types and of different power on the same vehicle model, as a function of the configuration of the vehicle. In fact, while the opacity of the glass of the rear window has an influence on the transmission of light from the stop light, the same applies to the radius of curvature and the inclination of the glass.
However, if different types of LEDs are used in the same embodiment of the stop light, there results a loss of efficiency. The device, and notably the optical lens, is generally adapted to suit a given type of LED or light source. The use of a different type of source for which the position of the optical lens has not been optimized beforehand generally generates sub-optimum behavior of the device.